Scanner for antenna system



Dec. 8, 1959 w. FALs-rRoM 'SCANNER FOR ANTENNA SYSTEM Filed July 28,1955 2 Sheets-Sheet 1 W. FALSTROM SCANNER FOR ANTENNA SYSTEM Dec. 8,1959 2 Sheets-Sheet 2 Filed July 28, 1955 d NM. u Il M d 5 l U17 ,Llr 7u f w n. 9 3 l, 69 5 9 n MJ. u w I l oo E .n r. 2q z 5|L a, B2 .u n

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United States Patent O SCANNER Fon ANTENNA SYSTEM William Falstrom, VanNuys, Calif., assignor, by mesne assignments to Underwoodv Corporation,New York, N.Y., a corporation of Delaware Application July 28, 1955,Serial No. 524,942

13 Claims. (cl.l 343-761) This invention relates to scanners suitablefor use with radio detection and ranging systems or thelike, and,particularly, to scanners capable of producing an elliptical-spiralscanning pattern.

The purposeof a scanner is to direct a beam of energy, such aselectromagnetic energy, into space and to make the beam trace aparticular pattern in space. The repeated tracing of the pattern isreferred to as scanning and the shape of the pattern characterizes thetype of scanning, such as circular, spiral, or linear.

A scanner `for radio detection and ranging system,

commonly referred to as a radar system, will include a feed or antennafor directing energy delivered to the feed by a transmission line towarda reflector. The reflector, which is usually parabolic in shape,formsthe `energy received from the feed into a beam and projects`"itinto space. The beam is moved inl space by moving the reflector or thefeed or both. The mechanism which produces these movements is referredto as `a scanner. l A circular scanning pattern, which is also referredto as a conical pattern, may be produced by locatingthefeed away fromthe directive axis of the reflector and rotating the feed about thedirective axis. The circular pattern'may also be produced by locatingthe feed away from the directive axis of the reflector and rotating thereflector about a line passing through the feed and the point where thedirective axis intersects the reflecting surface of the reflector,`which may be called the feed axis.' In both cases, the beam will trace acircular pattern'in space having the directive axis of the reflector asa center. y

When the angle between the feedaxis and thedirective axis is changed,the size of the circular pattern will change correspondingly, and ifthisangle is changed while the reflectoris rotating, a spiral patternwill be produced. The changing of this angle by a pivotal motionof therellector is referred to as nodding the `reflector.

In some radar applications, the target or search area is confined to thehorizon and the ideal scanning pattern would be a long thin rectangle.It is an object of this invention to provide a scanner in which thereliector is nodded and both the feed and the reflector are rotated,producing an elliptical-spiral pattern. `Itis a further object of theinventiongto provide such a scanner which utilizes relatively lowrotational velocities, thereby permitting use of a small, light weightand rigid structure that is easily dynamically balanced.

Another object of the invention is to provide a scanner having multiplescanning patterns, such as circular, spiral, elliptical-spiral andlinear, and in which the scanning pattern may be changed rapidly andsimply.

A further object of the invention is to provide a multiple patternscanner in which the pattern changing means does not disturb the dynamicbalance of the scanner.

' A nv important object of the invention is to provide a scanner inwhich the horizontal axis of the pattern is maintained horizontal whilethe structure in which the 2,916,739 `Patented Dec. 8, 1959 rtion andnovel combinations and arrangements of parts,

which will more fully appear in the course of the following description.However, the drawings merely show and the description merely describespreferred embodiments of the present invention as applied to a radarscanner, which are given by way of illustration or example only.

In the drawings: y

Fig. 1 is a sectional view of an embodiment of the invention;

Fig. 2 is` aside view taken along the line 2-2 of Fig. 1; l

Fig. 3 is a sectional view of another embodiment of the invention;

Fig. 4 is a sectional view taken along the line 4-4 of Fig. 3; and

Fig.V 5 is. a sectional view taken along the line 5 5 of Fig. 3 showingthe cam follower inphantom.

In `the embodiment of Fig. l, the moving elements of the scanner aresupported from a base 110. A frame 11 is rotatably mounted in the base10 by a bearing `12, the frame 11 being provided with a peripheral gearVvA drive. motor` 14 is mounted on the base 10, therotating shaft of thedrive motor carrying a pinion 1S which engagesthe peripheral gear 13.

A rellector 16, shown with the outer portion thereof broken away, ispivotally mounted on the frame 11 by pins 17, 18. The reflector 16 has aconcave inner surface 21 which is usually parabolic in shape andwhichhas anaxis of symmetryor directive axis 22. The frame 11 hasV an axis ofrotation 23 and the reflectorlis mounted on` the frame so that the pivotaxis of the reflector through the pins 17, 18 is normal to the planeoccupied` by the directive axis 22 and the axis `of rotation 23.

A countershaft 24 is rotatably mounted in a boss25 which extendsfrom theframe 11. Spur gears 26 and 27 and a worm 28 f are affixed to thecountershaft 24,A the worm 28 engaging ,a worm gear 31 that is mountedVon a crankshaft 32,. The crankshaft 32 is mounted in the frame 11 and isprovided V`Witha crankpn 33, the crankpin 33 engaging one end of a drivelink 34. A crankarm 35 is pivotally mounted on the pin 17 one arm of thecrankarm engaging the other end of the drive link 34 and the other annof the crankarrn being affixed toa boss 36 on the reflector 16.

A cluster gear 40 comprising a shaft 41 and gears 42 and 43, isrotatably mounted in a boss 44 extending from the base 10, the gear 43engaging the gear 26. A stabilization drive motor 45 is mounted ontherbase 10, a pinion 46 being mounted tothe rotating shaft of the drivemotor 45 and engagingthe gear .42. A spurlgear 47 is mounted on a shaft48 and engages the spur gear 27, the shaft being rotatably mounted in` aboss 50 which extends from the frame 11. A universal joint 51is'rnounted on the shaft 4S with its pivot axis coinciding with thepivot axis of the pins 17, 18, the universal joint 51 extending throughan opening SZin the reliector 16. p

A length of waveguide 53 is coupled to another length of waveguide 54which is coaxialwith the axis of rotation 23, by a rotating waveguidejoint 55. The waveguide 54 is rigidly joined to a length of waveguide 56which is supported by the frame'11. A'length of waveguide 58'issupported by the reector 16 at a shoulder 60 and is coupled to thewaveguide 56 by a rotating waveguide joint 61. A feed 62 comprising awaveguide doughnut antenna isv positioned in front of the reflectingsurface 21 of the reector 16 by a length of waveguide 63 which ismounted on an end 64 of the universal joint 51 and is coupled to thewaveguide 58 by a rotating waveguide joint'65. When the reflector 16 ispivoted on the frame 11, the feed 62 will also be pivoted about the axisthrough the pins 17, 18 due to the fact that the waveguide 58 is mountedon the retlector at the shoulder 60. When it is desired that the feed 62remain iixed relative to the axis of rotation 23 while the reflector ispivoted, the rotating joint 61 may be eliminated and the waveguide 58may be directly coupled to and supported by the waveguide 56.

The drive motor 14 rotates the frame 11 and the rellector 16 about theaxis of rotation 23, driving through the pinion 15 and the peripheralgear 13. Assuming for the moment that the cluster gear 40 is xedrelative to the frame 11, the countershaft 24 is driven from the gear 43by the rotation of the frame 11. The countershaft 24 in turn drives theshaft 48 through the gears 27, 47 and rotates the feed 62 about thedirective axis 22 in a direction opposite to that of the frame andreflector. The countershaft 24 also drives the shaft 32 through the wormand gear combination 28, 31, the rotation of the crankshaft 32 producingan oscillating movement of the crankarm 35 and the reflector 16 aboutthe pivot pins 17, 18. A second position of the oscillating reflector 16is shown in phantom in Fig. 2 and a second position of the rotating feed62 is shown in phantom in Fig. l.

A line 66 through the center of the feed 62 and the center of theuniversal joint 51 may be defined as a feed axis. When the feed axis 66is displaced from the directive axis 22 of the reflector 16, as shown inthe embodiment of Fig. l, and the feed is maintained fixed with respectto the reflector, rotation of the frame 11 with the reflector maintainedxed relative to the frame will produce a circular scanning pattern. Ifthe reflector is pivoted with respect to the frame while the frame isbeing rotated, the radius of the previously mentioned circular scanningpattern will be continually changing, and hence a spiral scanningpattern will be produced. When the pivoting motion of the reflector issuch that its directive axis oscillates between the lines indicated bynumerals 22 and 22 of Fig. 2, a doughnut-shaped area will be covered bythe scanning pattern. In the above discussion it has been presumed thatthe feed 62 has been maintained fixed relative to the reector 16. Whenthe feed is rotated about the directive axis 22 by the gearingpreviously described in a direction opposite to that in which thereector rotates, the previously described doughnut spiral pattern willbe changed to an elliptical-spiral pattern and the area scanned will bea solid ellipse when the angles formed by the axes 22, 22 with the axis23 are suitably chosen. The ratio of the major axis of the ellipse tothe minor `axis of the ellipse is a function of the ratio of the anglebetween the feed axis 66 and the directive axis 22 and the angle betweenthe directive axis 22 and the axis of rotation 23. When these angles areequal, the ellipse will be reduced to a straight line, producing alinear scanning pattern.

When a scanner with a spiral scanning pattern is used to cover an arealying along the horizon, it is essential that the major axis of theellipse lie along the horizon.

.When the scanner is mounted in a xed position, this may be accomplishedby simply changing the relative rotation angle between the moving parts.However, when the scanner is mounted in a moving vehicle, such as anairplane or a ship, the base 10 does not remain xed relative to thehorizon and some form of continuous stabilization is essential. In theembodiment of Fig. l, means are provided for stabilizing the maior axisof the elliptical-spiral scanning pattern even though the vehicle onwhich the base 10 s mounted is oscillating or rolling with respect tothe horizon. A roll correction signal is produced by a conventional typeof roll-sensing device, such as a gyroscope and servomechanism, notshown, and the correction signal is coupled to the stabilization drivemotor 45. When the major axis of the elliptical-spiral scan coincideswith the horizon, that is, when the feed and the reflector' have thedesired rotation angle relationship, there is no output from thestabilization drive motor 45 and the cluster gear 40 remains iixed.However, when there is an error due to the rolling of the base 10 withrespect to the horizon, there is an output from the stabilization drivemotor 45 which rotates the cluster gear 40 to change the rotationalangular relation between the feed and the reflector, thereby bringingthe major axis of the ellipticalspiral pattern into alignment with thehorizon as desired. This type of stabilization system is extremelysimple, the only additional parts required in the scanner being thedrive motor 45 and the gears 42, 46. This is an improvement overprevious types of stabilization systems which required that the base 10and the entire scanner be mounted on a plaform which was in turn mountedon the vehicle, the platform with the complete scanner thereon beingstabilized by tilting the platform with respect to the vehicle. y

In Fig. 3, another embodiment of the invention similar to that of Fig. 1is illustrated, like parts in the two embodiments being identified bythe same numerals. This embodiment differs from that of Fig. l in thatenergy is fed to the feed 62 through a different path, a differentmethod of coupling the drive motor to the pivoting reflector is providedand means are provided for shifting the elliptical-spiral scanningpattern to a circular scanning pattern.

The waveguide 53 is coupled to a length of waveguide 70 by the rotatingwaveguide joint 55, the waveguide 70 being rotatably mounted in an axialopening 71 in the frame 11. The frame 11 is provided with an extension72 that is rotatably mounted in the boss 44, the cluster gear 40rotating freely on the extension 72 and being spaced from the boss 44and the frame 11 by washers 73, 74. The retiector 16 is mounted on abase plate 75, a friction bearing 78 being mounted in the base plate 75along the directive axis 22. One end of the waveguide 63 is positionedwithin the friction bearing 78 and is coupled to the waveguide 70 by alength of flexible waveguides 76. A anged collar 77 is mounted on thewaveguide 70 by suitable means, such as welding, and a gear 80,corresponding to the gear 47 of Fig. l, is retained in place on theflanged collar 77 by a bushing 81 and a set screw therein, not shown. Aslip clutch comprising a coil spring 82 mounted on the anged collar 77and engaging a groove in the gear 80, couples the gear 80 to the collar77.

The groove in the gear 80 is shaped so that when .the gear is driven inone direction by the countershaft 24, the gear will engage the end ofthe spring 82 and the .gear 80, the flanged collar 77 and the waveguide70 will rotate in unison, thereby driving the feed 62 through thefriction bearing 78 in a direction opposite to that in which the frame11 is rotating. When the direction of rotation of the frame 11 and hencethe countershaft 24 is reversed, the end of the spring 82 is disengagedfrom the groove in the gear 80 and the gear 80 turns freely on the angedcollar 77 without imparting any rotational motion to the feed. Hence,when the direction of rotation of the frame 11 is reversed, thereiiector and the feed are rotated in unison by the friction bearing 78.

The worm gear 31 is mounted on a shaft 83 which is rotatably mounted inthe frame 11. A cam 84 having cam surfaces 85, 86 is mounted on theshaft 83 (Fig. 5), the cam surface 86 corresponding to the periphery ofthe shaft 83 in the embodiment of Fig. 3. The reector 16 and the baseplate 75 are mounted on a yoke 87 which is pivotally mounted on theframe 11 by the pivot pins 17, 18. A balance weight 90 is mounted on onearm of the pulley 92 and tends to rotate the pivot pin 17. This torqueapplied by the belt rotates the counterbalanced yoke 87 until the camfollower 91enga`g`es oneof the cam surfaces 85, 86. The rotation of theshaft 83 also rotates the cam 84, thereby causing the yoke 87 and thereilector 16 to pivot about the frame as a function of the shape of thecam surfaces .on the cam 84. The gearing of the embodimentof Fig. 3 isarranged so that when the reflector is rotated in one direction alongwith the frame, the feed is rotated in the opposite direction by actionof the slip clutch and the cam follower 91 is urged against the camsurface 85, therebypivoting the reflector with respect to the frame andproducing the desired ellipticalspiral scanning pattern. Whenthedirection of rotation of the frame is reversed, 'the feed and thereflector will rotate in unison and `the camffollower 91 will be urgedagainst the cam surface 86 thereby retaining the reflector fixed withrespect vto the frame and producing a circular scanning pattern. `Itshould be noted thatthis shift from'one type of scanning patterntolanother isv accomplished by reversing the direction of the drive`motor 11S and that it does not require anymechanical shifting of themoving components of the scanner and hence does not affect the dynamicbalance of the scanner structure.

In the embodiment of Fig. 1, the crankshaft 32 and its associatedcomponents produce a sinusoidal oscillation of the reflector 16 withrespect to the frame 111. The carn surface 85 of the embodiment of Fig.3 will produce saw-tooth oscillation of the reflector with respect tothe frame 11. The particular pattern of oscillation desired will dependupon the application to which the scanner is to be made; however, it isseen that any type of oscillation maybe achieved by providing a suitablecam surface on the cam 84.

If the cam surface 86 was similar in shape to that of the cam surface85, the reversing of the drive motor 14 would shift the scanning patternfrom elliptical-spiral to circular-spiral. In one instance the feed andreflector would be counterrotating and the reflector would be pivoted bythe cam surface 85 providing the ellipticalspiral pattern, in the secondinstance the feed and the reflector would be rotating in unison and thereflector would be oscillated by the cam surface I86, providing thecircular-spiral pattern. y

Although the above embodiments of the invention have been described inconjunction with waveguide for transmitting electromagnetic energy tothe antenna 62, it is clear that other means of transmission such ascoaxial conductors may be utilized and that a source or a sensing devicefor sound, heat, light, or other forms of radiation may be substitutedfor the antenna at the feed 62, thereby providing a scanner suitable fortransmitting and/or receiving any type of radiation. l

Although several exemplary embodiments of the invention have beendisclosed and discussed, it will be understood that other applicationsof the invention are possible and that the embodiments disclosed may besubjected to various changes, modifications and substitutions withoutnecessarily departing from the spirit of the invention.

I claim as my invention:

1. In a scanner, the combination of: a frame; a reflector pivotallymounted on said frame, said reflector having an axis of symmetry; drivemeans coupled to said frame for rotating said frame and reflector; afeed having an axis of rotation parallel with said axis of symmetry,said feed being positioned in front of said reflector so as to directradiated energy toward said reflector; and power means coupled to saidfeed for rotating said feed incontrolled relation to saidrotating frameand reflector for producing a predetermined scanning pattern.

2. In a scanner, the combination of: a frame; a reflector pivotallymounted on said frame; drive means coupled to said frame for rotatingsaid frame and reflector; a feed positioned in front of said reector soas to direct radiated energy toward said reflector; and means couplingsaid feed to said drive means for rotating said feed in synchronism withsaid frame and reflector for producing a predetermined scanning pattern.

3. A scanner as defined in claim 2 in which said frame and said feedrotate inlopposite directions at the same angular velocity relative tosaid drive means.

4. In a scanner, the combination of: a frame; a reffector pivotallymounted on said frame; drive means coupled to said frame for rotatingsaid frame andreilector; a feed positioned in front of said reflector soas to direct radiated energyV toward said reflector; and power meansrotating said feed in controlled relation to said frame and reflectorfor producing a predetermined scanning pattern.

5. In a scanner, the combination of: a frame; a reflector pivotallymounted on said frame; drive means coupled to said frame for rotatingsaid frame and reflector; means coupling said reflector lto said drivemeans whereby said reflector may be oscillated with respect to saidframe while said frame and reector are rotating; a feed positioned infront of said reflector so as to direct radiated energy toward saidreflector; and means coupling said feed to said drive means for rotatingsaid feed in controlled relation to said frame and reflector forproducing a predetermined scanning pattern.

6. In a scanner, the combination of: a frame; a reflector pivotallymounted on said frame, said reflector having a directive axis; drivemeans coupled to said frame for `rotating said frame and reflector; afeed rotatably and pivotally mounted on said frame, said feed having anaxis of rotation coaxial with said directive axis; means coupling saidreflector to said drive means whereby said reilector may be oscillatedwith respect to said frame while said frame and reflector are rotating;and power means for rotating and oscillating said feed in controlledrelation to said frame and reflector for producing a predeterminedscanning pattern.

7. In a scanner, the combination of: a base; an antenna having areflector element and a feed element mounted for rotation relative toone another; a first drive motor mounted on said base; a differentialgear unit having first, second and third couplings, the rotation of saidfirst coupling relative to the rotation of said second coupling being afunction of the rotation of said third coupling; a first power gear unitconnecting said first drive motor to one of said antenna elements and tosaid first coupling, said first drive motor rotating said one elementrelative to said base; a second power gear unit connecting the other ofsaid antenna elements to said second coupling; and a second drive motormounted on said base and connected to said third coupling for varyingthe rotation of said other antenna element relative to said one antennaelement.

8. A scanner as defined in claim 5, in which said means coupling saidfeed to said drive means includes differential means, and power meansfor actuating said differential means in response to an externalreference signal, said differential means varying the relative rotationof said feed and said frame.

9. A scanner as defined in claim 6, in which said frame and said feedrotate in opposite directions at the same angular velocity relative tosaid drive means and in which said reflector and said feed oscillate inphase.

10. In a scanner, the combination of: a frame; a reflector pivotallymounted on said frame; a cam mounted on said frame and having two fixedcam surfaces; reversible drive means for rotating said cam; a camfollower coupled to said reflector and engaging said cam for os- '7cillating said reflector Aas said cam rotates; and means driven by said-drive means for urging said cam follower against `one .of said camsurfaces when Ydriven in one direction and against the other of said camsurfaces when driven .in Athe lopposite direction.

1l. In a scanner, the combination of: aframe; a reector pivotallymounted on said frame; a -cam mounted on said Aframe and havingconcentrically positioned cam surfaces fixed relative to each other;reversible drive means for rotating said cam; a cam follower vpivotallymounted on said frame ,and coupled to said reector for engaging said camand oscillating said reflector as said cam rotates; ,and a slippabledrive system coupling said -drive means to said .cam follower for urging.said -cam follower ,against one of `said cam surfaces when driven inone 4direction and against the other of said cam surfaces when `drivenin the opposite direction.

12. In a roll compensated scanner, the combination of: a housing formounting on/a vehicle which may be rolling; areector; rst drive meansmounted on said housing and coupled to said reflector for continuouslyrotating said reflector .at a predetermined speed; a feed positioned in.front of said reflector so as to direct radiated energy tosaid feed andreector without .changing said predetermined speeds. i. y ,y I

13. In a roll .compensated scanner, Ithe vcombination of: a housing formounting ,on a vehicle lwhich may be rolling; a rector; first drive,means mounted on ,said housing and coupled to said reiiector for,continuously rotating said reflector at a predetermined speed about anaxis; a feed positioned lin rfront of said reector so as to directradiated energy toward said reector; a vcountershaft carried on saidreflector -for rotation about said axis with said reector, saidcountershaft being rotatably mounted for rotation relative to saidreector also; a roll reference gear carried on said housing, with said,countershaft coupling said free to said reference gear for continuouslyrotating `said ,feed relative to said reector at ,a predetermined speed;and second drive means mounted on .said housing for varying the angularposition of said reference gear in response to the rolling of tthevehicle for hanging the angular relation between saidfeed ,andyreflector without changing said predetermined speeds.

References Cited in the ile of ,this patent UNITED S'1`ATESff/PATENTS2,437,275 Skene et al. Man 9, 1948 2,512,139 Cady 4 June 2Q, 19502,526,314 Alexanderson et al. v Oct. 17, 1950 2,537,822 Fritts Jan. 9,r1951 2,543,188 Moseley n Feb. 27, 195-1 2,678,394 Curtisk u May 1l,1954 UNITED STATES PATENT OFFICE CERTHCATE 0F CORRECTION Patent Nm2,916,739 eeember 8, 1959 William Falstrom It is herebjr Certified thaterror appears in theprnted specification of the above numbered patentJrequiring correction and that the said Letters Patent should read ascerrectaed below.`

Column 8, line 14, for "free" read wfeed no Signed and sealed the 17thdey of Mey 19H3.,

(SEAL) Attest:

KARL Ll AXLINE ROBERT C. WATSON Attesting Ocer Commissioner of Patents

